Cheap and easy possibility for at 2-3 portables--your dashboard air vents.
This works best if:
-The vents are slanted 45 degress or less from vertical
-The vents can be turned on or off individually (you don't want hot or cold air constantly blowing on your radios)
-The vents are rectangular wth lots of parallel slats as opposed to circular with large, coarse slats
Take a piece of heavy wire such as coathanger and bend it so that it will present a hanger about the width of your belt clip, and with a couple of small hooks that will attach either to the vent's horizontal slats, or the vertical supports behind them.
I do this in rental cars all the time. You can make custom hooks in no time flat with a pair of cutting pliers. (I use a leatherman tool) In most cases, they're easy to remove. If too hard to remove, just cut them in half and they come out with a half-twist.
I prefer using cheap coathangers with a dark plastic coating--it looks more dignified when the radios aren't mounted. I just hang the portables, and they are readable and manipulable without taking my eyes off the road. Rubber duckie antennas at windshield level work great in most localities that use trunked or other repeater systems. I can install and remove the radios instantly with no worries about power lines or coax. Even at night with their dial lamps on, they aren't that noticable from the outside, and I once removed 3 portables as I anticipated being stopped by a tailgating police car. The officer made no inquiry.
I also prefer to run the radios on NiMH rather than car power. It keeps the batteries cycled, and avoids my chief source of electrical noise. Of course, I also carry a charger and spare alkaline packs. The rapid charger is quite noisy, and I like to keep it in the rear floor, and plugged into the rearmost outlet I can find.
This is a great setup for taking a trip and collecting data. With newer radios such as the PSR-500, you can save must new data by pushing one button, and note-taking is minimal to non-existant. During the week, I do the same thing with my air vents and dashboard cup holder.
Easy, removable, and leaves no scars.
73/Allen (N4JRI)
PS - if your airvents are more angled from vertical, it's best to increase the length of your hooks so that the radio comes out farther from the dashboard and can hang at a more vertical angle.